The present invention relates to a mass spectrometer and a method of mass spectrometry. The preferred embodiment relates to a mass spectrometer comprising tandem ion traps.
Various ion trapping techniques are well known in the field of mass spectrometry. For example, commercial 3D or Paul ion traps are known which comprise a central ring electrode and two end-cap electrodes. Linear geometry or 2D linear ion traps (LIT) are also known which comprise a quadrupole rod set and two end electrodes for confining ions axially within the ion trap.
It is known to trap or confine ions within an ion trap by applying inhomogeneous fields modulated at radio frequencies to the electrodes comprising the ion trap. DC trapping potentials may also be applied to some of the electrodes in order to confine ions axially within the ion trap. It is known to mass selectively eject ions from ion traps in either a radial or axial direction using a variety of different techniques.
However, known commercial ion traps suffer from the problem of having a relatively limited dynamic range. The relatively limited dynamic range is due to the onset of space charge saturation effects which occur when relatively high density ion populations are stored simultaneously within the ion trap. Space charge saturation effects in analytical ion traps have the effect of causing a loss in analytical performance. In particular, mass resolution, mass measurement precision and precision of quantitation may be reduced. Furthermore, as mentioned above, space charge saturation effects reduce the dynamic range of mass spectra which can be produced using the ion trap.
It is therefore desired to provide an improved mass spectrometer and method of mass spectrometry.